In systems marking receiving members, such as paper products, Mylar and other flexible media, the paper sometimes jams in the travel path and disrupts or stops the entire marking system. In some systems used today, manual clearing of these jams is used with manual access to the sheet transport used. Included in “marking machines” are printers, copiers, fax, and other paper handling marking machines or systems.
For purposes of clarity, the system of the present invention will be described in reference to an electrostatic marking system; however, any marking systems where paper or other flexible media are transported internally are included within the scope of this invention.
In one embodiment where the process of electrostatic reproduction is used, a light image of an original to be copied or printed is typically recorded in the form of a latent electrostatic image upon a photosensitive member with a subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual toner image can be either fixed directly upon the photosensitive member or transferred from the member to another support medium such as a sheet of plain paper. To render this toner image permanent, the image must be “fixed” or “fused” to the paper, generally by the application of heat and pressure.
With the advent of high speed Xerography, or other marking machines wherein these machines can produce at a rate in excess of three thousand copies per hour, there is a need for a reliable sheet-handling system. For example, this reliability is needed in systems feeding paper or other media through various processing stations in a rapid succession. This is important to utilize the full capabilities of the relatively expensive marking machines. These sheet-handling systems must operate flawlessly to virtually eliminate risk of damaging the receiving sheets and generate minimum machine shutdowns due to paper jams, misfeeds or multifeeds. Jamming can occur for a variety of reasons, such as worn nips in rollers, moisture, faulty sensors and, in some cases, can be due to up curl and down curl in sheets which generally occur randomly in the document stack. With the high speed marking machines used today, rapidly traveling paper along a paper path that is, for some reason, interrupted by a paper jam can cause significantly longer and more damage and downtime than in heretofore slower systems.
As noted, earlier in marking machines, paper jams have long been a serious problem and have become a more serious problem in today's high-speed machines. When a paper jam occurs, the entire marking system is down costing the user valuable time and expense until the jam is fixed. Heretofore, various manual strategies and features have been developed to reduce the occurrence of jams and to minimize the burden on the user to recover from the jam. Some of these strategies include: early detection of fault conditions; controlled cycle down and cycle up of machines; manually purging “bad” sheets which may be damaged or out of sequence to a destination where they are easily recognized and separated from “good” sheets and minimizing the number of steps and the number of sheets and the difficulty of removing paper from the jammed machine.
In some instances, sheets not affected or downstream from the jam can be delivered as good and reusable and sheets upstream from the jam must be maintained in the system apart from the jammed sheets. Purged sheets must then be recognized by the user as “bad” and discarded using an output destination, such as a “purge tray”.
Incorporated by reference herein is U.S. Pat. No. 4,078,787 which discloses a paper jam technique in a copier that causes a complete shutdown of the machine. Copier jam recovery is accomplished by manually opening the machine access covers, removing the jammed sheets and closing the covers. In U.S. Pat. No. 4,231,567, a method and apparatus for clearing jams in the transport path of a copier includes the steps of sensing a jam, clustering in-process sheets either at the jam location or at an area upstream of the jam location while simultaneously allowing sheets downstream of the jam location to continue.
In U.S. Pat. No. 6,010,127, a buckle chamber is provided along a sheet path where jammed sheets are compiled during a down cycle during a paper jam.
Usually, a jam in a marking machine or printer is defined as a sheet or sheets of paper in the paper path which has either stayed too long at one station (sensor), or has not reached the next station (sensor) within a pre-defined specific period of time. These conditions are determined by optical sensors used where each sheet in the path is sensed and, because of these sensors, the machine subsequently will be able to detect automatically if the self-clearing action was effective. Once a jam is detected in a marking machine the system shuts down and an operator is instructed to clear the jammed sheet and the remaining paper from the machine. The machine will “wait” until the paper path has been successfully cleared by the operator prior to attempting to restarting the job. The present invention provides that once a jam condition is detected and the system has shut down, the machine itself will automatically attempt to clear the jammed sheet(s) and any other sheets in the paper path. This would be accomplished by at least part of the paper path automatically reversing itself (i.e. at least some of the drive motors are run in the reverse direction) for a predetermined time while baffles are used or gates are actuated to direct the “jammed” sheets out of the paper path and into a waste area for disposal later (or exit the machine). The baffles are passive and need not be actuated, whereas the gates need to be actuated. This procedure will occur in even unattended marking machines. Once the machine has successfully cleared itself of the jammed and other sheets, it would automatically restart the job and resume normal operations. This would allow the operator to have the machine function unattended and return to pick up their completed job at a later time without having to worry about the possibility of jamming and not completing their job. If the machine attempted several times to clear the jam and was unsuccessful, it would declare a continuing jam and the operator would be instructed how to clear the jam in the usual manual manner.